Heterocyclic Antioxidants in Nature: Coumarins

Coumarins represent an important family of naturally occurring and/or synthetic oxygen-containing heterocycles, bearing a characteristic benzopyrone framework. These compounds are widely distributed both in human diet and therapeutics. Among other characteristics, several coumarin derivatives proved to have an interesting antioxidant profile. In the current review, an overview of the role of natural coumarins as important antioxidants is presented and discussed. The benefits of antioxidants to prevent chronic diseases is also discussed in the current review. The most common assays performed to evaluate the antioxidant capacity described in this review are related to different reactive oxygen species involved in the oxidative process. Several reaction mechanisms were studied to investigate the antioxidant profile of coumarins. Among them, hydrogen atom transfer (HAT) and single electron transfer transfer (SET), were highly cited. To make the organization of this overview as clear as possible, coumarin derivatives were dived in: simple coumarins; aliphatic, terpenoid and aromaticcontaining coumarins; ring-fused coumarins and ellagic acid derivatives.